Lessons Learned From Another Sprout Recall

Jim Prevor’s Perishable Pundit, June 10, 2009

In the midst of our extensive coverage of the industry problems with alfalfa sprouts, we received word of another sprout-related recall. We asked Pundit Investigator and Special Projects Editor Mira Slott to find out more:

Sidney ChangOwnerChang FarmWhatley, Massachusetts

Q: What instigated your company recall of bean and soy sprouts? How and where was the Listeria monocytogenes discovered?

A: A State of New York inspector took a sample at a retail store that also manufactures product there. It’s a wholesaler/retailer/manufacturer in Chinatown basically.

Q: Was the sample from your product? How do the inspectors know the contamination originated from your product and not from the retail facility or somewhere along the distribution chain? Have FDA and New York State been forthcoming in releasing documentation linking the positive back to Chang Farm?

A: In the beginning, they really didn’t specify the kind of sprout. Eventually, I got a photo of the product — the sample in the laboratory, just for my own personal information. I can tell a bean from soybean sprouts. It was a soybean sprout, a bulk product with no labeling on it. We encourage our customers to sell packaged product for retail, and bulk for people that supply restaurants. We can’t really tell them what to do, and some people sell loose. This sample definitely came from product that was sold loose.

Wednesday May 27, five people from FDA and three from the State of Massachusetts came here and investigated for two days. They basically looked at my facility and took samples everywhere. I read through some of the paperwork and signed a form that showed FDA took at least 150 or more samples. And the State collected another 100 samples. They said if I have this Listeria monocytogenes, they’ll find it. So far the test results showed nothing. It’s not official on letterhead yet, but they came and closed my case, and basically they should know if there’s a presumptive positive in three days. They have verbally confirmed no Listeria monocytogenes was found in my products or at the facility. I am waiting for it to be official. Believe me, they’d tell me to make a full scale recall right now if they found anything.

When we launched our business, we didn’t start in a converted warehouse or basement. We started selling bean sprouts in 1983 after we built a brand new facility, and we expanded it in 1998. We started with 7,200 square feet, added 6,400 square feet in 1998, and this year we’re taking a big jump to 30,000-plus square feet. The place is more than double the size of the old plant.

Q: How extensive are your own testing procedures for catching pathogens?

A: We followed FDA recommendations to test for E. coli 0157 and Salmonella in our product irrigation water. FDA doesn’t recommend any testing for Listeria. Each company has its own program. Usually it’s swabbing of the facility but not on product. That’s the practice we used. Right now we’re reevaluating all our pathogen testing, and will definitely incorporate Listeria testing in spent irrigation water.

Q: What kind of seed treatments do you use? FDA suggests 20,000 ppm calcium hypochlorite in its guidance for reducing microbial food safety hazards for sprouted seeds. However, some industry executives are opposed to this treatment because of its toxicity and potential risks to employees. What is your position?

A: We sanitize with calcium hypochlorite, but we do use a different formulation. At the moment, we use calcium hypochlorite, but I don’t want to comment on how much. In the near future, we will be changing our seed treatment utilizing hot water for pasteurizing the seed, which would be environmentally friendly and much safer on employees.

Calcium hypochlorite at high levels is very dangerous to handle. If an employee has a cut in the glove or it rolls down the side of the glove, it will burn your skin, and it will sting your eyes. FDA is recommending 20,000 ppm calcium hypochlorite as a main solution, but in Japan, they do things differently.

In the U.S., bean sprouts are very small in volume. In Japan, bean sprouts are like the fresh-cut salads industry the U.S. Many factories are producing ½ million pounds of sprouts a day. At Japanese retailers, bean sprouts take up the equivalent of U.S. supermarket space devoted to the bagged salad displays. The Japanese obviously know a lot more than I do about bean sprouts. That’s why I’m going to Japan — to buy all new equipment for our new building.

In Japan, they use heat to kill bacteria. Technically, there shouldn’t be contamination beneath the skin; it’s a very unlikely scenario. The seed is very hard and can withstand a lot of heat and can kill bacteria under the skin if there was some.

A: It’s exactly the same process as what they use to pasteurize almonds. Seed is dipped in several chambers of water. For example, mung beans may start at 60 degrees, room temperature. The first chamber may be 100 degrees, and then the beans are dipped in another chamber that may be 180 degrees. The temperatures do vary depending on the seed varieties, reaching around 187 degrees. It’s a high temperature, but not boiling.

The product is submerged and vigorously agitated in very sophisticated equipment. It looks like a giant latte machine. Tanks inject high temperature steam and need to maintain temperatures for enough time to kill bacteria. Then another chamber is used to cool product back down and then it can be used for sprouting.

Q: Pasteurization doesn’t harm the integrity of the product?

A: There is no damage to the seed, but timing is very precise. There’s a formula at what temperature it needs to hit and for what duration to get 5 log reductions. They adjust to different varieties. We’re going to use pasteurization on mung beans and soy beans. It’s a widely used practice in Japan. It is all computer-controlled with formulas to accommodate different sizes and varieties.

Q: Could there be complications in using pasteurization for alfalfa seed? Why isn’t this process being widely used in the U.S. right now? Should FDA revise its industry guidance?

A: A modified version of this machine could be used for alfalfa, but I don’t know that much about treatments for alfalfa seed.

[Editor’s note: Industry executives say the pasteurization method developed and used extensively in Japan is very effective for mung beans, but has posed difficulties with different types of seeds. For example, certain temperatures won’t penetrate into a big seed, but in smaller seeds will kill it. Pasteurization of alfalfa seeds has shown promise in scientific testing, but there are still issues to overcome in maintaining the seed integrity.]

Q: As the industry forges ahead with strategies to improve food safety, could we revisit what precipitated your recent recall of bean and soy sprouts? Did FDA or New York State share more detail on discovery of the Listeria contamination at the wholesale/retail facility in Chinatown and how they concluded the problem originated at your company, the methodology for testing, etc.?

A: They won’t release the sample. It was found outside the facility, so how do we know it didn’t come from cross contamination? The field agents that came here to investigate were professional and treated me well. They were feeling that after all this happened, it would be important to question the person who collected the sample, which tested positive.

The agents that came here don’t know the methods of sampling, but they are beginning to question the process. I don’t have to make a further recall; that’s the key. If my facility was contaminated, they should find problems in the product very easily.

Q: Alas, large numbers of negative tests in a facility don’t necessarily disprove that contaminated product came from that facility at another time… I understand that Listeria monocytogenes is not typically associated with sprout recalls. Is this an isolated incident or have you had to deal with other food safety problems in the past?

A: It’s happened to us twice; Last year, Listeria monocytongenes was found in a retail grocery store. I was notified three weeks after the sell-by-date had expired. These products are very perishable. This was also from the State of New York, in New York City, and I believe they found the contamination in a package of our bean sprouts. There was no recall done because product was so out of date. They sent people to my facility to inspect, and went to another store in Massachusetts and collected samples, and in two of those, they found Listeria monocytogenes.

Listeria monocytogenes is broken down into subgroups. Some subgroups are deadly. This one is not deadly. It can make someone sick or cause them discomfort, but it won’t kill. I’m not a scientist, but I believe Listeria m subgroups in produce are usually non-virulent. In dairy and in meat, they can be deadly. Dr. Kendra Nightingale is an expert in this area and will be speaking at the ISGA Convention in Chicago.

[Editor’s note: See interview with Dr. Kendra Nightingale below, where she clarifies and elaborates on what is known regarding contamination of Listeria monocytogenes in food products].

Finding it twice in the last two years is definitely hurting us a lot. We are staying on top of the newest methods, and building better, more modern facilities. The laws have changed in development of food safety manufacturing plants. People have learned a lot over the years and we’re getting the latest technology. Our new building should be up and running by late fall, early winter.

One key insight from this interview: Sprouts are a fringe industry in the U.S., but a mainstay in Japan. If we follow Japanese food safety practices, we may be able to end this scourge of sprout-related outbreaks in the U.S.

Many thanks to Sidney Chang and Chang Farms for helping the industry consider this important matter.

We wanted to get more information on the science surrounding this matter. Mira followed up with the expert Kendra Nightingale mentioned:

[Editors’ note: Dr. Nightingale will be speaking on June 19th at the ISGA Convention in Chicago]

Q: Could you share your expertise in the study of Listeria monocytogenes contamination in foods? We hope to gain a better scientific understanding of the types of strains and their prevalence and interaction in produce.

A: Listeria monocytogenes is the only species in the Listeria genus that is pathogenic to humans. Within L. monocytogenes, different strains appear to differ in the likelihood and relative ability to cause human disease. A few specific L. monocytogenes strains or serotypes (i.e., serotypes 1/2a, 1/2b and 4b) cause the majority (90%) of human illnesses and one specific serotype (i.e., serotype 4b) has been associated with the majority of listeriosis outbreaks worldwide.

While we have not been able to identify pathogen factors associated with enhanced virulence (or ability to cause disease), a large component of my research program at Colorado State University has been focused on the identification and characterization of mutations leading to attenuated virulence (or reduced ability to cause disease) in L. monocytogenes. However, we do not yet have precise information regarding the distribution of strains associated with the majority of illnesses and outbreaks or strains with attenuated virulence with respect to different food categories.

Q: For perspective, has there been research documenting how often deadly strains show up in different types of food products?

A: Results from my laboratory show that a significant proportion of L. monocytogenes strains carry virulence attenuating mutations in inlA, a key L. monocytogenes virulence gene that facilitates crossing of the intestinal and possibly placental borders during an infection. We have developed a molecular assay that detects these virulence attenuating mutations in inlA and it is our hope that this assay will be used in the future by regulatory agencies to make science-based decisions regarding the presence of L. monocytogenes with defined virulence characteristics (e.g., whether or not a strain carries a virulence attenuating mutation in inlA) in ready-to-eat foods. [Read study here.]

Q: Is there information specific to produce?

A: We recently used this molecular assay to screen more than 500 L. monocytogenes isolates from ready-to-eat foods for the presence of virulence attenuating mutations in inlA and preliminary results show that 45% of food isolates carry virulence attenuating mutations in inlA. Some of these food isolates were from bagged salads; however, other RTE food products categories were also included (e.g., deli meats, deli salad, smoked seafood and cheeses). Additional analyses will be required to probe associations between virulence attenuating mutations in inlA and different food categories.

Q: In the produce industry, it is much more common to see recalls and outbreaks associated with E. coli and Salmonella, with Listeria problems focused in meat and dairy items. Why is that?

A: We haven’t done much in the past with regard to routine testing and surveillance for L. monocytogenes in produce. L. monocytogenes is ubiquitous in nature and is thus routinely isolated from soil, surface water, vegetation and manure. L. monocytogenes can also be present in the environment of the food processing plant and cross-contamination of food products after processing is thought to be the major route of finished product contamination. As a result, I don’t think it is entirely surprising that L. monocytogenes could be present in produce.

Q: According to Sidney Chang of Chang Farms, the sample New York State inspectors collected, which tested positive for L. monocytogenes, came from loose product in a wholesale/retail facility in Chinatown. He believes the finding could have been a result of cross-contamination.

A: That is a definite possibility.There are many opportunities for contamination to happen at the retail level.

Q: With the lack of Listeria testing in produce, do you think data and general perceptions are distorted on which products carry greater risk for contamination of Listeria monocytogenes?

A: That is one possibility. The current FDA/USDA:FSIS/CDC risk assessment for L. monocytogenes estimates that nearly 90% of listeriosis cases are attributed to consumption of contaminated deli meats. However, declines in the prevalence of L. monocytogenes in deli meats and the incidence of listeriosis over recent years have not paralleled each other, suggesting that other food categories or distribution of strains with enhanced or attenuated virulence in different food categories could play a more important role in the food attribution of listeriosis than currently recognized. More research is needed to determine what those food product categories could be and how strains with defined virulence characteristics are distributed among different food categories.

It is hard to know what to make of seemingly random findings of ubiquitous pathogens.Yet the findings — and the associated recalls and bad publicity — are of such great effect, we can’t ignore these issues either.

Many thanks to Professor Nightingale and Colorado State University for helping us to better understand this complicated issue.